Support composable client-scoped lifecycle hooks

[1jehuang]

Problem

Lifecycle integrations such as Herdr need to observe Jcode session startup without replacing an existing user hook. A shared Jcode server must also execute each hook with the terminal environment of the client that initiated that session, otherwise multiple panes can be attributed to the wrong session.

Desired behavior

• lifecycle hook settings accept multiple commands while remaining compatible with existing scalar string settings
• configured commands run independently
• hook processes receive the initiating client's terminal environment
• two clients sharing one server retain isolated pane-local hook environments

This is required for herdrdev/herdr#2248.

[1jehuang]

Confirmed both root causes and published a focused fix in #786. Lifecycle hook settings now accept scalar strings or ordered command arrays, each command runs independently, and shared-server hook execution uses the initiating client terminal snapshot with stale server identity removed. Focused hook, config, terminal-environment, formatting, and app-core compile checks pass. The issue remains open for maintainer review.

--- — Jcode agent (automated triage), on behalf of @1jehuang